1. Technical Field
The present invention relates to a vehicle headlight provided to a vehicle such as an automobile, and particularly relates to a vehicle headlight that reduces the contrast above and below a cutoff line and prevents a driver of a vehicle from feeling a sense of incongruity and to a vehicle headlight that reduces the contrast above and below a cutoff line and prevents a driver of other vehicles from being dazzled.
2. Related Art
A headlight of a vehicle such as an automobile projects light emitted from a light source such as, for instance, an incandescent light bulb, discharge lamp, and LED with a projection optical system such as a projector and a reflective optical system such as a reflector.
With such a headlight, switching is possible between a driving beam (high beam) for use during normal driving and a passing beam (low beam) for use when passing an oncoming vehicle.
In order to prevent glare that dazzles an oncoming driver, a cutoff line is formed in a predetermined range at the upper edge of a light distribution pattern for the passing beam, such that light is substantially not radiated above the cutoff line.
In such a headlight, it is known that a desired light distribution pattern is formed through collaborative use of a plurality of light sources or optical systems.
For instance, Japanese Unexamined Patent Application Publication (JP-A) No. 2011-3515 describes that a main light distribution pattern or the like having a cutoff line is formed by a projector unit and a diffused light distribution pattern is formed by a reflector unit.
JP-A No. 2011-161035 describes that a part of a beam emitted by a light source of a projector unit is guided to a reflector by a mirror member to illuminate a shoulder or the like on the driving lane side.
JP-A No. 2001-195910 describes a technique in which an auxiliary light distribution pattern for a passing beam from a projector unit is formed by an auxiliary reflector.
In a technique disclosed in JP-A No. 2001-195910, a cutoff line formed by a projector unit is illuminated, with an auxiliary light distribution pattern formed by a reflector unit, on both the left and right sides (oncoming side and non-oncoming side) of an elbow point arranged in the middle.
A projector unit using a projection optical system is advantageous in space efficiency since the configuration is relatively compact. However, since a clear cutoff line is formed due to the structure, a driver may feel a sense of incongruity in the contrast above and below the cutoff line.
By illuminating the vicinity of the cutoff line of the projector unit with a reflector unit that uses a reflective optical system capable of a relatively moderate change in luminance around a light distribution pattern to reduce the contrast above and below the cutoff line, it is possible to reduce the sense of incongruity in a driver.
However, in the case where the cutoff line on the left and right sides of the elbow point is illuminated with the reflector unit as with the technique disclosed in JP-A No. 2001-195910, light is distributed additionally to a region that is already illuminated uniformly with a main light distribution pattern on the non-oncoming lane side (vehicle side) of the elbow point, and a resulting non-uniformity of the light distribution pattern on a road surface may cause a driver to feel a sense of incongruity.
In the case where the vicinity of the cutoff line is illuminated by the reflector unit, light is radiated above the cutoff line to some degree. Therefore, a driver of an oncoming vehicle or a preceding vehicle may be dazzled by the glare.